Sensing cavitation-related events in artificial lift systems

ABSTRACT

Methods and apparatus are provided for sensing a cavitation-related event in an artificial lift system for hydrocarbon production and operating the system based on the sensed event. One example method of operating an artificial lift system for a wellbore generally includes monitoring the wellbore for an indication (e.g., an acoustic or vibrational indication) of an event associated with cavitation in the artificial lift system and adjusting at least one parameter of the artificial lift system if the event is detected. One example system for hydrocarbon production generally includes an artificial lift system for a wellbore and at least one sensor configured to detect an indication of an event associated with cavitation in the artificial lift system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application for Patent claims priority to U.S. Provisional Application No. 62/216,812, filed Sep. 10, 2015, which is assigned to the assignee of the present application and hereby expressly incorporated by reference herein in its entirety.

BACKGROUND

Field of the Disclosure

Certain aspects of the present disclosure generally relate to hydrocarbon production using artificial lift and, more particularly, to sensing an event associated with cavitation in an artificial lift system.

Description of the Related Art

Several artificial lift techniques are currently available to initiate and/or increase hydrocarbon production from drilled wells. These artificial lift techniques include rod pumping, plunger lift, gas lift, hydraulic lift, progressing cavity pumping, and electric submersible pumping, for example.

Sensors are often used to monitor various aspects when operating artificial lift systems. For example, U.S. Pat. No. 6,634,426 to McCoy et al., entitled “Determination of Plunger Location and Well Performance Parameters in a Borehole Plunger Lift System” and issued Oct. 21, 2003, describes monitoring acoustic signals in the production tubing at the surface to determine depth of a plunger based on sound made as the plunger passes by a tubing collar recess.

SUMMARY

Certain aspects of the present disclosure provide a method for operating an artificial lift system for a wellbore. The method generally includes monitoring the wellbore for an indication of an event associated with cavitation in the artificial lift system and adjusting at least one parameter of the artificial lift system if the event is detected.

Certain aspects of the present disclosure provide a system for hydrocarbon production. The system generally includes an artificial lift system for a wellbore and at least one sensor configured to detect an indication of an event associated with cavitation in the artificial lift system.

According to certain aspects, the sensor is configured to detect the event before the cavitation occurs in the artificial lift system.

[000s] According to certain aspects, the artificial lift system includes a downhole fluid pump disposed in the wellbore. For certain aspects, the fluid pump is a hydraulic jet pump. In this case, the hydraulic jet pump may include a nozzle and a throat, wherein fluid is passed through the nozzle into the throat. Cavitation damage may occur to the throat. For certain aspects, the sensor is coupled to the downhole fluid pump.

According to certain aspects, the artificial lift system includes a power fluid pump.

According to certain aspects, the system further includes a wellhead. For certain aspects, the sensor is positioned at the wellhead.

According to certain aspects, the sensor is positioned in the wellbore.

According to certain aspects, the event comprises an onset of cavitation occurring or actual cavitation occurring.

According to certain aspects, the indication is an acoustic or vibrational indication having a frequency of about 5.6 kHz.

According to certain aspects, the sensor comprises at least one of a microphone, an accelerometer, or a gyroscope.

Certain aspects of the present disclosure provide a sensor configured to detect an indication of an event associated with cavitation in an artificial lift system.

According to certain aspects, the sensor is configured for coupling to a wellhead of the wellbore. For other aspects, the sensor is configured for positioning in the wellbore. For example, the sensor may be configured for coupling to a fluid pump of the artificial lift system.

According to certain aspects, the sensor comprises a microphone, an accelerometer, or a gyroscope.

Certain aspects of the present disclosure provide an apparatus for operating an artificial lift system for a wellbore. The apparatus generally includes means for monitoring the wellbore for an indication of an event associated with cavitation in the artificial lift system; and means for adjusting at least one parameter of the artificial lift system, if the event is detected.

Certain aspects of the present disclosure provide a non-transitory computer-readable medium containing a program. The program, when executed by a processing system, causes the processing system to perform operations generally including monitoring a wellbore for an indication of an event associated with cavitation in an artificial lift system and adjusting at least one parameter of the artificial lift system, if the event is detected.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to certain aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a conceptual illustration of an example artificial lift system with a cavitation sensor, in accordance with certain aspects of the present disclosure.

FIG. 2 depicts an example downhole portion of an artificial lift system with a cavitation sensor, in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates an example cavitation sensor connected with a processing system, in accordance with certain aspects of the present disclosure.

FIG. 4 is a conceptual illustration of an example fluid pump for an artificial lift system, in accordance with certain aspects of the present disclosure.

FIG. 5 is a flow diagram of example operations for controlling an artificial lift system, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

Certain aspects of the disclosure provide techniques and apparatus for monitoring a wellbore for an indication of an event associated with cavitation in an artificial lift system and adjusting at least one parameter of the artificial lift system if the event is detected.

FIG. 1 is a conceptual illustration of an example artificial lift system 100. The artificial lift system 100 includes a wellhead 102 coupled to production tubing 104 disposed downhole in a wellbore 114 and surface machinery 106, generally located at the surface of the wellbore. A downhole fluid pump 110 may be disposed in the production tubing 104 in a downhole portion 116 of the artificial lift system 100, while at the surface, a surface controller 107 and a power fluid pump 112 may be coupled to the wellhead 102. The power fluid pump 112 may force power fluid down the production tubing 104, and, in response, the downhole fluid pump 110 may force hydrocarbons back up the tubing 104 towards the surface.

Artificial lift systems (e.g., system 100) may suffer from production problems associated with cavitation. Cavitation occurs when negative gage pressure vapor filled bubbles form in wellbore fluid and higher pressure in the fluid surrounding the bubbles causes the bubbles to implode violently. Bubbles can form, for example, when a pump intake is starved for fluid or when localized fluid pressure drops below the vapor pressure of the solution. Micro-jets that may be due to the bubble implosions can cause severe damage to artificial lift system components. In some cases, incorrect pump selection (e.g., selecting a pump that generates enough suction at the pump intake to lower pressure below the vapor pressure of the solution) can lead to cavitation. In other cases, altered well conditions (e.g., a change in the fluid entering the pump intake) can lead to cavitation. Cavitation may damage or even destroy pumps, thereby reducing artificial lift system efficiency and sometimes completely disabling an artificial lift system.

At least two events can be associated with cavitation: onset of cavitation (also referred to as “incipient cavitation”) and cavitation. Onset of cavitation occurs before cavitation and may be accompanied by an acoustic indication, such as a loud, high-pitched noise or a vibrational indication. As an example, the acoustic indication may have a frequency of about 5.6 kHz, where “about” as used herein generally refers to a range within ±20% of the nominal value. During onset of cavitation, fluid conditions are nearly ripe for cavitation to begin occurring, but no cavitation-related pump damage has occurred. However, once cavitation occurs, pump damage may be certain and nearly instantaneous, resulting in a substantial reduction in hydrocarbon production efficiency.

Under current artificial lift system operating procedures, cavitation is only detected post hoc (i.e., after cavitation has already occurred); there is no procedure for detecting onset of cavitation. The only indication of a cavitation event is a drop in production efficiency, and the system production rate may fall significantly, sometimes to zero. In any case, the system may have to be shut down or set to a maintenance mode to allow for repairs, e.g., to a pump or other artificial lift equipment. Before production at full capacity can be resumed, the downhole fluid pump may be drawn out of the wellbore, and damaged pump components may be replaced by other components (or the entire pump may be replaced). This typically involves waiting for the replacement components to be shipped, which can result in significant system downtime and production loss.

Losses due to cavitation can be reduced if system operating parameters can be adjusted to prevent cavitation before the cavitation occurs. Accordingly, techniques and apparatus for detecting cavitation or an onset of cavitation in an artificial lift system and adjusting one or more parameters of the artificial lift system to avoid cavitation damage and production losses are desired.

According to aspects of the present disclosure, to help prevent production loss associated with cavitation, the artificial lift system 100 may include at least one sensor 108, which may be positioned at and acoustically, mechanically, and/or otherwise coupled to the wellhead 102, for example. The sensor 108 is configured to detect an indication of an event associated with cavitation (e.g., that actual cavitation is occurring or an onset of cavitation). For example, the sensor 108 may be a microphone, an accelerometer or other vibrational sensor, or a gyroscope configured to detect vibrations or other indications of cavitation. The sensor 108 may be capable of detecting an indication associated with actual cavitation and/or an indication associated with the onset of cavitation and sending a signal (e.g., to the surface controller 107 or another control system of the artificial lift system 100). The signal may be an electrical signal conveyed via a wire or wirelessly and/or an optical signal (e.g., a light pulse) conveyed via an optical waveguide (e.g., an optical fiber). In cases where the sensor 108 detects an indication associated with the onset of cavitation, the sensor 108 may be instrumental in helping prevent cavitation in the artificial lift system 100. For example, a control system and/or an operator of the artificial lift system 100 may adjust a parameter (e.g., decrease a flow rate), to prevent cavitation in the artificial lift system 100, in response to a signal from the sensor 108. Alternatively, in cases where the sensor 108 detects an indication associated with actual cavitation, the sensor 108 may be useful in helping prevent further damage to the system 100. For example, a control system and/or an operator of the artificial lift system 100 may adjust a parameter (e.g., inspect a pump for damage, replace a pump component, etc.), to prevent further cavitation in the artificial lift system 100, in response to a signal from the sensor 108.

FIG. 2 depicts an example downhole portion 202, such as the downhole portion 116, of an artificial lift system, such as the artificial lift system 100. However, instead of or in addition to at least one sensor positioned at the wellhead 102, at least one sensor 204 may be coupled to the downhole portion 202 such that the sensor 204 is positioned downhole in the wellbore. The sensor 204 may be coupled to the downhole portion using any of various suitable mechanisms, such as one or more clamps, a bolted-on arrangement (as shown in FIG. 2), one or more tie-wraps, and the like. In some aspects, the downhole portion 202 may be a downhole fluid pump, such as the downhole fluid pump 110 shown in FIG. 1, and at least one sensor 204 may be positioned at, above, and/or below the downhole fluid pump.

Similar to sensor 108, sensor 204 is configured to detect an indication of an event associated with cavitation in the artificial lift system. For example, the sensor 204 may be a microphone, an accelerometer, or a gyroscope configured to detect sound or vibration. The sensor 204 may detect an indication associated with onset of cavitation, and/or an indication associated with cavitation. In cases where the sensor 204 detects an indication associated with onset of cavitation, the sensor 204 may help prevent cavitation in the system by detecting onset of cavitation and sending a signal (e.g., to a control system of an artificial lift system) indicating the onset of cavitation before cavitation occurs. The signal may be an electrical signal conveyed via a wire or wirelessly and/or an optical signal (e.g., a light pulse) conveyed via an optical waveguide (e.g., an optical fiber). A control system and/or an operator of the artificial lift system may respond to the signal by adjusting a parameter of the artificial lift system to prevent cavitation from occurring. Alternatively, in cases where the sensor 204 detects an indication associated with cavitation, the sensor 204 may help prevent further damage to the artificial lift system by sending a signal indicating that cavitation is occurring. The signal may be an electrical signal conveyed via a wire or wirelessly and/or an optical signal (e.g., a light pulse) conveyed via an optical waveguide (e.g., an optical fiber). A control system and/or an operator of the artificial lift system may respond to the signal by adjusting a parameter of the artificial lift system to prevent further cavitation from occurring.

FIG. 3 depicts a sensor 300 for transducing properties of an environment (e.g., vibrational or acoustic energy) into electrical or optical signals. The sensor 300 includes communication lines 302, 304 for conveying information from the sensor 300. For example, communication line 302 may transmit the electrical or optical signals to a processing system 306 (e.g., with signal processing, analog-to-digital converting, memory storing, and data manipulating capabilities), such as the surface controller 107. Communication line 304 may be used to receive signals from another sensor in some aspects, while in other aspects, communication line 304 may be omitted. Furthermore, the sensor 300 is configured to be positioned to detect an indication of an event associated with cavitation in an artificial lift system of a wellbore. For example, the sensor 300 may be configured for coupling to a wellhead. Alternatively, the sensor 300 may be configured for positioning in the wellbore. In this case, the sensor 300 may be configured for coupling to a fluid pump of the artificial lift system, as described above.

FIG. 4 is a conceptual illustration of an example fluid pump for an artificial lift system, in accordance with certain aspects of the disclosure. The fluid pump may be any of a variety of fluid pumps including a hydraulic jet pump 402 as depicted. The hydraulic jet pump 402 includes a nozzle 404, a throat 406, and one or more production inlet chambers 408.

As an example operation of the fluid pump, the hydraulic jet pump 402 may be disposed in a wellbore, and power fluid may be pumped down the wellbore towards the hydraulic jet pump 402. Initially, the fluid may have a high pressure and low velocity. However, the nozzle 404 may constrict the flow of the power fluid, drastically increasing the power fluid's velocity and decreasing its pressure. This power fluid may then jet through the nozzle 404 into the throat 406. In some cases, the power fluid jetted from the nozzle 404 is at a lower pressure than production fluid in the production inlet chambers 408. The pressure gradient between the production inlet chambers 408 and the throat 406 can result in production fluid flowing into the throat. This may result in production fluids intersecting and mixing with power fluid.

The intersecting and mixing of fluids in the throat 406 may result in conditions that can lead to cavitation, as described above regarding cavitation-associated events. For example, fluid conditions and/or the nozzle-throat size combination may lead to cavitation-associated events, which may damage the throat 406.

As described above, an event associated with cavitation may be accompanied by an indication. For example, a cavitation-associated event at the throat 406 of the hydraulic jet pump 402 may lead to vibration of the fluid pump. In turn, the fluid pump vibration may lead to an indication 410 (e.g., an acoustic or vibrational indication). The indication 410 may have a frequency of about 5.6 kHz, for example. The indication 410 may be conveyed to a sensor, such as sensor 108, 202, or 300. In some aspects, the indication 410 travels up the wellbore to the sensor at the wellhead, where the sensor detects the indication 410. In other aspects, the sensor is disposed in the wellbore, and the indication 410 travels along the wellbore to the sensor. Alternatively, the sensor may be strapped to the fluid pump (as shown in FIG. 2) and directly detect the indication 410.

Operating an Artificial Lift System

FIG. 5 is a flow diagram of example operations 500 for controlling an artificial lift system for a wellbore, in accordance with certain aspects of the disclosure. Performing the operations 500 may prevent cavitation damage from occurring to a fluid pump, such as the fluid pumps described above. In some cases, performing the operations 500 can prevent cavitation damage from occurring to a throat of a hydraulic jet pump, such as the throat 406.

The operations 500 may begin, at block 502, by monitoring a wellbore for an indication of an event associated with cavitation in an artificial lift system. At block 504, at least one parameter of the artificial lift system may be adjusted if the event is detected. The event may, for example, be onset of cavitation, or the event may be cavitation. Additionally, the indication may have a frequency of about 5.6 kHz, for example.

Monitoring at block 502 may include using one or more sensors to detect the indication. For example, the sensor(s) may be sensor 108, 204, or 300, as described above. Thus, the sensor(s) may include a microphone, an accelerometer, and/or a gyroscope. Additionally, similar to aspects described above, the sensor(s) may be positioned at a wellhead for the wellbore and/or in the wellbore. As described regarding FIG. 2, the sensor(s) may be coupled to a fluid pump of the artificial lift system.

Adjusting at block 504 may include changing any of various suitable parameters of the artificial lift system, such as replacing or repairing equipment or components; modifying, introducing, or removing control signals; storing and/or reporting the indication; setting a flag and/or outputting a signal based on the indication; and the like. Outputting a signal may include, for example, generating an analog or digital signal and transmitting the signal via a wire, wirelessly (e.g., via a radio transmission), and/or as one or more light pulses conveyed via an optical waveguide (e.g., an optical fiber). Other examples of outputting a signal include generating an audible sound, turning on a light, and/or causing a message to appear on a display screen.

For certain aspects, at least one parameter can be adjusted to avoid cavitation damage. These adjustments can be made before cavitation occurs in the artificial lift system, such as during onset of cavitation, or after cavitation occurs. For example, the parameter may be a production rate by the artificial lift system. In such aspects, adjusting may include increasing production, reducing production, or stopping production of the artificial lift system. If production is stopped, it may be helpful in certain situations to wait a sufficient time before resuming production for fluid to settle in the wellbore.

In some circumstances, such stop-and-go operation may not be sufficient to resolve the event. For example, the event may be occurring due to improper throat sizing and/or cavitation damage to the fluid pump. In any case, adjusting the parameter may include removing the fluid pump of the artificial lift system from the wellbore. The fluid pump can then be inspected for cavitation damage. If the damage is present, the fluid pump or one or more components thereof can be replaced. Alternatively, the adjusting may include replacing at least one component of the fluid pump with another component to avoid cavitation damage in subsequent wellbore operation. For example, the fluid pump may be a hydraulic jet pump, as depicted in FIG. 4. In such cases, the throat installed in the fluid pump may be replaced with a new throat that has a different size than the installed throat. The different size throat may cause flow (e.g., of a power fluid and production fluid mixture) through the hydraulic jet pump to be altered from flow through the original throat in such a manner that cavitation does not occur.

Any of the operations described above, such as the operations 500, may be included as instructions in a computer-readable medium for execution by the surface controller 107 or any suitable processing system. The computer-readable medium may comprise any suitable memory or other storage device for storing instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, an electrically erasable programmable ROM (EEPROM), a compact disc ROM (CD-ROM), or a floppy disk.

While the foregoing is directed to certain aspects of the present disclosure, other and further aspects may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. 

1. A method for operating an artificial lift system for a wellbore, comprising: monitoring the wellbore for an indication of an event associated with cavitation in the artificial lift system; and adjusting at least one parameter of the artificial lift system if the event is detected.
 2. The method of claim 1, wherein the event comprises an onset of the cavitation occurring.
 3. The method of claim 1, wherein the event comprises the cavitation occurring.
 4. The method of claim 1, wherein the monitoring comprises using at least one sensor to detect the indication.
 5. The method of claim 1, wherein the adjusting comprises removing a fluid pump of the artificial lift system from the wellbore.
 6. The method of claim 5, wherein the adjusting further comprises: inspecting the fluid pump for cavitation damage; and if the damage is present, replacing the fluid pump or one or more components of the fluid pump.
 7. The method of claim 5, wherein the adjusting further comprises replacing at least one component of the fluid pump with another component to avoid cavitation damage in subsequent wellbore operation.
 8. The method of claim 7, wherein the fluid pump is a hydraulic jet pump, the at least one component is a first throat, the other component is a second throat, and the second throat has a different size than the first throat.
 9. The method of claim 1, wherein the adjusting is performed before the cavitation occurs in the artificial lift system.
 10. The method of claim 1, wherein the at least one parameter comprises a production rate by the artificial lift system.
 11. The method of claim 1, wherein the adjusting comprises stopping production by the artificial lift system.
 12. The method of claim 11, further comprising resuming production after a sufficient time for fluid to settle in the wellbore.
 13. The method of claim 1, wherein the adjusting comprises outputting a signal.
 14. A system for hydrocarbon production, comprising: an artificial lift system for a wellbore; and at least one sensor configured to detect an indication of an event associated with cavitation in the artificial lift system.
 15. The system of claim 14, wherein the at least one sensor is configured to detect the event before the cavitation occurs in the artificial lift system.
 16. The system of claim 14, wherein the artificial lift system comprises a downhole fluid pump disposed in the wellbore.
 17. The system of claim 16, wherein the downhole fluid pump is a hydraulic jet pump that comprises a nozzle and a throat, wherein fluid is passed through the nozzle into the throat.
 18. The system of claim 16, wherein the at least one sensor is coupled to the downhole fluid pump.
 19. The system of claim 14, further comprising a wellhead, wherein the at least one sensor is positioned at the wellhead.
 20. The system of claim 14, wherein the at least one sensor is positioned in the wellbore.
 21. The system of claim 14, wherein the event comprises an onset of the cavitation occurring.
 22. The system of claim 14, wherein the at least one sensor comprises at least one of a microphone, an accelerometer, or a gyroscope.
 23. A non-transitory computer-readable medium containing a program which, when executed by a processing system, causes the processing system to perform operations comprising: monitoring a wellbore for an indication of an event associated with cavitation in an artificial lift system; and adjusting at least one parameter of the artificial lift system, if the event is detected.
 24. The computer-readable medium of claim 23, wherein the event comprises an onset of the cavitation occurring.
 25. The computer-readable medium of claim 23, wherein the event comprises the cavitation occurring.
 26. The computer-readable medium of claim 23, wherein the program causes the processing system to perform the adjusting before the cavitation occurs in the artificial lift system.
 27. The computer-readable medium of claim 23, wherein the at least one parameter comprises a production rate by the artificial lift system.
 28. The computer-readable medium of claim 23, wherein the adjusting comprises stopping production by the artificial lift system.
 29. The computer-readable medium of claim 28, wherein the operations further comprise: resuming production after a sufficient time for fluid to settle in the wellbore.
 30. The computer-readable medium of claim 23, wherein the adjusting comprises outputting a signal. 